Chapter 17 Mandatory Access Control

Table of Contents
17.1 Synopsis
17.2 Key Terms in This Chapter
17.3 Explanation of MAC
17.4 Understanding MAC Labels
17.5 Planning the Security Configuration
17.6 Module Configuration
17.7 The MAC seeotheruids Module
17.8 The MAC bsdextended Module
17.9 The MAC ifoff Module
17.10 The MAC portacl Module
17.11 The MAC partition Module
17.12 The MAC Multi-Level Security Module
17.13 The MAC Biba Module
17.14 The MAC LOMAC Module
17.15 Nagios in a MAC Jail
17.16 User Lock Down
17.17 Troubleshooting the MAC Framework
Written by Tom Rhodes.

17.1 Synopsis

FreeBSD 5.X introduced new security extensions from the TrustedBSD project based on the POSIX®.1e draft. Two of the most significant new security mechanisms are file system Access Control Lists (ACLs) and Mandatory Access Control (MAC) facilities. Mandatory Access Control allows new access control modules to be loaded, implementing new security policies. Some provide protections of a narrow subset of the system, hardening a particular service. Others provide comprehensive labeled security across all subjects and objects. The mandatory part of the definition comes from the fact that the enforcement of the controls is done by administrators and the system, and is not left up to the discretion of users as is done with discretionary access control (DAC, the standard file and System V IPC permissions on FreeBSD).

This chapter will focus on the Mandatory Access Control Framework (MAC Framework), and a set of pluggable security policy modules enabling various security mechanisms.

After reading this chapter, you will know:

Before reading this chapter, you should:

Warning: The improper use of the information contained herein may cause loss of system access, aggravation of users, or inability to access the features provided by X11. More importantly, MAC should not be relied upon to completely secure a system. The MAC framework only augments existing security policy; without sound security practices and regular security checks, the system will never be completely secure.

It should also be noted that the examples contained within this chapter are just that, examples. It is not recommended that these particular settings be rolled out on a production system. Implementing the various security policy modules takes a good deal of thought and testing. One who does not fully understand exactly how everything works may find him or herself going back through the entire system and reconfiguring many files or directories.

17.1.1 What Will Not Be Covered

This chapter covers a broad range of security issues relating to the MAC framework. The development of new MAC security policy modules will not be covered. A number of security policy modules included with the MAC framework have specific characteristics which are provided for both testing and new module development. These include the mac_test(4), mac_stub(4) and mac_none(4). For more information on these security policy modules and the various mechanisms they provide, please review the manual pages.